Torque overload clutch coupler for a torque transmitting driveline

ABSTRACT

A torque overload coupler for a driveline allows limited free motion. In one embodiment, torque overload protection is provided by a friction slip clutch and tangs formed at the inner perimeter of a clutch plate fit into spaces between lugs defined on a hub to provide a limited range of free motion. In another embodiment, torque overload is provided by a shear pin and free motion is provided by the shear pin fitting into angular spaces between wings of a relatively rotatable hub.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to torque transmitting couplings for drive-linesand in particular to a torque transmitting coupling which providestorque overload protection and a limited range of free motion.

2. Discussion of the Prior Art

In connecting a driveline between a driven shaft and a driving shaft,both of the shafts may be difficult to turn so that aligning them tomake the connection is very difficult. For example, in connecting theuniversal joint of an agricultural implement to the power take-off shaftof a tractor, there is a problem in aligning the splines of theimplement shaft with the splines of the tractor's power take-off shaft.To overcome this problem, it is known to provide a free motion devicewhich allows limited rotation between the two ends of the device so thatthe splines can be aligned.

It is also desirable in some applications, to limit the torque which canbe transmitted by the driveline. Several methods of doing this areknown, including friction clutches which slip when the torque becomestoo great, and also shear devices are known in which a shear pin issheared off when the torque exceeds a certain level.

Heretofore, the capability of a limited degree of free motion and torqueoverload protection have been provided in separate devices. The presentinvention addresses this issue.

SUMMARY OF THE INVENTION

The invention provides a torque overload coupler for a torquetransmitting driveline which efficiently and economically provideslimited free motion and torque overload protection in a single,self-contained unit. In one aspect, first means for connecting thecoupler to a torque input shaft and second means for connecting thecoupler to a torque output shaft have a bearing between them forallowing relative rotation and fixing them axially. A clutch housing isfixed to the first connecting means and a clutch plate in the clutchhousing which engages the housing has tangs defined at an innerperimeter with interstitial angular spaces between the tangs. Lugs aredefined on the second connecting means which extend radially into theinterstitial angular spaces and are smaller in angular extent than theinterstitial spaces. The first means can therefore rotate relative tothe second means through an angle which is limited by the lugs abuttingthe tangs to allow alignment when the coupler is being connected betweentwo shafts, and the clutch plate slipping relative to the clutch housingprovides torque overload protection. In this aspect, a pressure plate ispreferably provided in the clutch housing which is biased against theclutch plate so that the clutch is normally engaged.

In another aspect, the invention provides a torque overload coupler fora torque transmitting drive-line with limited free motion and shearjoint torque overload protection. In this aspect, a radially extendingflange is formed on the first connecting means in axially facing contactwith a surface of the second connecting means, and the flange definesaxially symmetrical wings having angular spaces between them. A shearpin is received in a hole in the surface of the second means and extendsfrom the surface into one of the angular spaces for side-to-sideabutment with sides of the wings, the shear pin being shearable by oneof the wings if a certain torque limit is exceeded.

Other objects and advantages of the invention will be apparent from thedrawings and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a free motion device of the invention shownattached to a driveline;

FIG. 2 is a partial sectional view of the device shown in FIG. 1, asviewed from the plane of the line 2--2 of FIG. 4;

FIG. 3 is a cross-sectional view of a clutch plate and hub for theinvention as viewed from the plane of the line 3--3 of FIG. 2 and shownin an engaged position;

FIG. 4 is a right end elevational view of the coupling shown without thecover plate or belleville spring and with the hub and clutch plate shownin a disengaged position;

FIG. 5 is a sectional view of a second embodiment of a torque overloadfree motion shear device of the invention;

FIG. 6 is an end view of the device of FIG. 5; and

FIG. 7 is a fragmentary view of an alternate embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a device 10 of the invention shown coupled to adriveline 12. The driveline 12 may be any type of driveline, for examplean industrial or an agricultural driveline, and may be provided with ashield or guard 13.

At one end of the driveline, a universal joint yoke 14 is secured to thedriveline and is rotatably secured to two arms of a universal jointcross 16, whose other two arms are rotatably secured to yoke 18, whichis part of the device 10. Yoke 18 has legs 19 (three of four are shown)which are fixed by bolts 20 to a clutch housing 22 which has coolingfins 24 on its front side and is covered on its back side by cover plate26, which is secured to the housing 22 by bolts 28.

Hub 30 is preferably internally splined as shown at 31 to mate with thesplines on a shaft to be connected to the hub 30 and may be slotted asshown at 33 and provided with bolts 32 for clamping it to the shaft tofix it axially, for example for clamping it to the implement gearbox orinput shaft or power take-off shaft of a tractor. A keyed connection orany other suitable rotary drive connection may alternatively be used.Hub 30 extends through hole 34 (FIG. 2) of plate 26 and, at the innerend of hub 30, an axially extending flange 36 is formed and defines anouter ball bearing race 38 on its inner diameter. A set screw 39 isscrewed radially into flange 36 and opens into the race 38 so that balls46 can be loaded into the race. It should be noted that the gap at 90(for example, 0.0025 inches) is preferably substantially smaller thanthe gaps at 91 (for example, 0.012 inches) to inhibit lubricant flowpast it. The axial length of the gap 90 (for example, 0.25 inches) andits smallness work as an effective seal, so that no additional seal,such as an O-ring, is necessary.

An inner bearing race 40 is formed in flange 42 of yoke 18, and greasefitting 44 in yoke 18 allows for lubrication of the balls 46 in theraceways 38 and 40. Accordingly, the anti-friction bearing provided bythe balls 46 in the raceways 38 and 40 allows for relative rotationbetween the yoke 18 and the hub 30, while fixing the yoke 18 and the hub30 together axially.

Radially outward of flange 36, a clutch plate 50 is received in a slightrecess on the inside axial face of the housing 22, which locates theplate 50 radially. The clutch plate 50 surrounds hub 30 and is providedwith facings 52 and 54 of friction material on its two axial faces,between housing 22 and pressure plate 56. Pressure plate 56 is biasedtoward clutch plate 50 by belleville spring 60 so as to compress theplate 50 and facings 52 and 54 between the pressure plate 56 and thehousing 22. Coil springs or other biasing means may also be used to biasthe plate 56.

Pressure plate 56 preferably has raised radially extending angularlyspaced ribs 57A and 57B (FIGS. 2 and 4) on its outer surface which pressagainst the spring 60 adjacent to the inside diameter of the spring 60so as to minimize the surface area of contact between the pressure plate56 and the spring 60, thereby minimizing heat transfer from the plate 56to the spring 60. This minimizes damage to the spring 60 from heat. Ribs57A stop at the inside diameter 59 of the plate 56 and ribs 57B riseaxially slightly at the inside diameter 59 to create shoulders 63 whichlocate the spring 60 on its inside diameter 61. Ribs 57B extend inwardof the inside diameter 59 to create a centrifugal fan for cooling of theunit. Also, open spaces 21 (two of four shown in FIG. 4) are definedbetween the legs 19 and the housing 22 through which air may be drawn bythe fan to cool the unit. Openings 23 are also preferably provided inthe side of the clutch housing 22 for cooling air flow.

On its outer perimeter, pressure plate 56 has ears 62 (FIG. 4) whichextend into spaces 65 defined between tongues 64 formed on the inside ofthe housing 22 so as to hold the housing 22 and pressure plate 56nonrotatable relative to one another, but allow them to move axiallyrelative to one another. The fit of the ears 62 in the spaces 65 neednot be tight, so as to allow for liberal manufacturing tolerances, sinceonce the ears 62 contact the tongues 64, they stay in that position,being substantially held against relative rotation by the frictionalengagement of the clutch plate 50.

The inside periphery 70 of the clutch plate 50 defines 3 equiangularlyspaced tangs 72 (FIG. 3) with angular spaces 74 defined between thetangs 72. Three equiangularly spaced lugs 76 are formed on the flange 36of hub 30 which extend into the spaces 74 and are of an angular sizesmaller than the spaces 74 so that the hub 30 may be turned byapproximately 60 degrees relative to yoke 18 (30° in either directionfrom being centered, as shown in FIG. 4) before the lugs 76 contact thetangs 72. This degree of angular freedom is sufficient in most cases toallow aligning the splines of the hub 30 with the splines of the shaftto which the hub 30 is to be connected, or, if the opposite end of thedrive-line is the last one to be connected, the alignment can be made atthat end as well. More or less than three tangs and nestled lugs may beused to practice the invention.

Under operation, when the device 10 is being used to transmit torque inthe operation of the driveline, the torque is transmitted by the lugs 76abutting the tangs 72 and is transmitted up to the torque value at whichslippage occurs between the clutch plate 50 and the housing 22 andpressure plate 56.

FIG. 5 illustrates a second embodiment of a device 100 of the invention.The device 100 has a yoke 118 which has a radially extending circularflange 119. An outer bearing race 138 is formed in the inside diameterof the flange 119 and an inner bearing race 140 is formed in the outsidediameter of hub 130. Thus, the bearing provided by balls 146 and races138 and 140 allows angular rotation between the hub 130 and yoke 118while fixing them axially relative to one another. A grease fitting (notshown) for lubricating the bearing could be provided in the flange 119,and any suitable means, for example similar to the set screw provided inthe first embodiment, could be provided, for example through flange 119,to load the balls 146 into the raceways 138 and 140.

A flange 151 is securely affixed to the hub 130 by weld 153, or othersuitable means, for example by being cast or formed integrally with thehub 130. The flange 151 is axially symmetrical and defines twosymmetrical wings 182 and 184. The wings 182 and 184 define between themangular spaces 174. A shear pin 175 extends into one (or both, althoughnot shown) of the angular spaces 174 and is positioned so as to abut oneof the surfaces 177 or 179, both of which are aligned along radiallines, should the hub 130 be turned relative to the yoke 118 byapproximately 60 degrees (30° in either direction from center).

As shown in FIGS. 5 and 6, the shear pin 175 is a bolt which is securedto the flange 119 by being inserted through a hole 181 in the flange 119and having a nut 183 securing it on the back side of the flange 119. Arecessed washer 185 may be provided at the head end of the bolt 175 sothat when the head 187 gets sheared off due to a torque overloadcondition, the metal of the flange 119 adjacent to the head 187 is notdamaged. In addition, the flange 119 may be heat treated to avoid damageto it. However, as shown in FIG. 7, the shear pin 175 could be a pinpressed into a bore in the flange 119, with or without (as shown in FIG.7) a surrounding washer.

Many modifications and variations to the preferred embodiments describedwill be apparent to those skilled in the art. Therefore, the inventionshould not be limited to the embodiments described, but should bedefined by the claims which follow:

We claim:
 1. A torque overload clutch coupler for a torque transmittingdriveline, comprising;first means for connecting said coupler to atorque input shaft; second means for connecting said coupler to a torqueoutput shaft; a bearing between said first and second connecting meansfor allowing free relative rotation between said first and secondconnecting means and fixing said connecting means axially relative toone another; a clutch housing fixed to said first connecting means; aclutch plate in said clutch housing for frictionally engaging saidclutch housing, said clutch plate having tangs defined at an innerperimeter thereof and interstitial angular spaces between said tangs;lugs defined on said second connecting means extending within saidinterstitial angular spaces and being smaller in angular extent thansaid interstitial spaces so as to allow a predetermined amount ofrelative rotation between said first and second connecting means;wherein said first connecting means can freely rotate withoutsubstantial torque resistance relative to said second connecting meansthrough an angle which is limited by said lugs abutting said tangs.
 2. Atorque overload clutch coupler as claimed in claim 1, wherein said angleis approximately 60 degrees.
 3. A torque overload clutch coupler asclaimed in claim 2, wherein three of said tangs and three of said lugsare provided.
 4. A torque overload clutch coupler is claimed in claim 1,further comprising a pressure plate in said clutch housing and meansbiasing said pressure plate against said clutch plate so that saidclutch coupler is normally engaged.
 5. A torque overload clutch coupleras claimed in claim 4, further comprising fins on said pressure plate incontact with said biasing means, said fins thermally isolating saidbiasing means from said pressure plate.
 6. A torque overload clutchcoupler as claimed in claim 1, wherein one of said connecting means is auniversal joint yoke.
 7. A torque overload clutch coupler as claimed inclaim 6, wherein the other one of said connecting means is an internallysplined collar.